Evaluation of hepatic iron concentration heterogeneities using the MRI R2* mapping method

Abstract Objective To measure hepatic iron concentration (HIC) heterogeneities using a magnetic resonance R2* mapping method. Patients and Methods Ninety-four patients with suspected hepatic iron overload and 10 volunteers were included prospectively. A multi-echo R2* sequence with fat saturation and with three post-processing fitting methods (a single exponential decay model with or without truncation, SED and SEDt, and a constant offset model, COS) was compared to a signal intensity ratio method (SIR), considered as the reference. HIC heterogeneity was evaluated from R2* mapping after placing a ROI on each liver segment. Results A strong linear correlation between SIR and R2* methods using the SEDt and COS models was observed (r = 0.973 and 0.955, respectively). Volunteers and patient liver variabilities, quantified by mean intra-liver standard deviation (SD) were 1.58  μ mol/g (mean range 5.06  μ mol/g) and 4.73  μ mol/g (mean range 19.08  μ mol/g), respectively. For the patient group, the highest HIC was observed in the IV th segment. Heterogeneity increased for patients with an HIC >60  μ mol/g (mean intra-liver SD = 13.90  μ mol/g; mean range = 50.60  μ mol/g). Conclusion This study is the first to demonstrate in vivo HIC heterogeneities using whole-liver mapping analysis. These preliminary results require confirmation through further studies, but might be useful in cases of single ROI analysis.